Major classes of inventories are presented below. Readily Marketable Inventories ("RMI") are agricultural commodity inventories such as corn, soybeans, wheat, and ethanol co-products, among others, carried at net realizable value which approximates fair value based on their commodity characteristics, widely available markets, and pricing mechanisms. The net realizable value of RMI is calculated as the fair value (spot price of the commodity in an exchange), less cost of disposal and transportation based on the local market. All other inventories are held at lower of cost or net realizable value.


(in thousands)	September 30, 2022		December 31, 2021		September 30, 2021
Grain and other agricultural products (a)	$	1,198,790	$	1,427,708	$	732,512
Propane and frac sand (a)	25,797		23,780		18,481
Ethanol and co-products (a)	117,310		184,354		105,052
Plant nutrients and cob products	214,529		178,696		161,759
Total inventories	$	1,556,426	$	1,814,538	$	1,017,804

(a) Includes RMI of $1,167.0 million, $1,410.9 million and $700.3 million at September 30, 2022, December 31, 2021 and September 30, 2021, respectively.

Inventories do not include 0.9 million, 3.0 million and 2.0 million bushels of grain held in storage for others as of September 30, 2022, December 31, 2021 and September 30, 2021, respectively. The Company does not have title to the grain and is only liable for any deficiencies in grade or shortage of quantity that may arise during the storage period. Management has not experienced historical losses on any deficiencies and does not anticipate material losses in the future.